running two tb6380 190kv on a dv6 with a Panasonic 21700 12s4p battery. i have a need for speed so i switched from tb110 wheels to trampa 165 mm urban treads and it still tops out at 40mph. i was hoping for more speed with the benefit of comfort with the pneumatics but now i just have a comfy board with kinda sad torque and nearly half the range. it went from 18/36 to 18/44 so i understand the torque loss but i figured if it could get up to 50ish the torque loss on these long, flat Midwestern roads wouldn’t be a big deal. im thinking its the battery because it’s supposedly rated for 70a max and im running it at 30 per side and it sags pretty bad with both wheels. but i would love a second opinion as im still fairly new to the diy esk8 world.
So you switched from a bad ratio to a slightly better ratio (more torque)
If I were you I would expect about the same speed, which is what you got, except you also switched to bigger wheels, which decreased the ratio even more
It doesn’t seem right for you to get that speed though I would expect higher
Plug in all your numbers here:
What’s it give you for Max Speed Loaded (at the very bottom)?
the ratio wasnt bad for what i use the board for. it’s a street board and there isn’t much stop and go around here. but yeah i expected a little more speed and for it to take a little longer to get there but it just doesn’t
i used it before i even bought the wheels because i was trying to figure out how to get more speed on 12s but my old setup was 40mph loaded and the new setup is 50mph loaded. i expected to at least get to 45 but it barely gets to 40 so something has to be bottlenecking right?
You are totally hitting some limit there that doesnt let you go faster as with that setup you should be able to hit 55mph. I think it has to do with a mix of voltage sag, and not getting enough current to the motors to fight air drag and rolling resistance at 40mph wich its pretty high.
i dont really go that fast so im just making an hypothesis
Probably the battery can’t supply enough current to overcome the wind resistance at that point with the new setup. Could you log a ride where you hit your top speed? The battery current value and the duty cycle, both at top speed, could indicate that you don’t have enough power. The voltage value at top speed could also be useful, as that battery is pretty badly sagging I imagine
Ditto this. If your battery can only output 5 kilowatts of power, then no gearing setup will let you exceed the point where air resistance demands 5 kilowatts. Be aware that the Esk8 calculator does not account for this fact.
The equation is Power = 0.3 * V^3 , very roughly, for an avergage size rider standing sideways. (V is in m/s)
im using xmatic so unfortunately i cant check for past rides but it sags down to less than half at full charge when im riding full out
Thats your problem right there
i thought so. just wanted to make sure. thanks everyone!
What cells are in the 12S4P battery? What are your maximum battery current settings?
This is like saying “a two wheel drive Ford car” but not specifying whether it’s a Mustang or Fiesta or something else.
im not sure. all i know is its a Panasonic 21700 4800mah cell. i asked boundmotor what cell type is was when i bought it so i could figure out the discharge for the vesc and all they said was 70a max and never told me the cell type. i set each side to 30a and just forgot about it. i guess i should probably open it up and see.
It’s a pretty mediocre cell if it’s what i suspect. These unlabeled panasonic 21700’s are really common on boards where they just want to advertise a huge wh capacity, but the actual output is pretty bad on them. I had one of those packs in an Eovan, and at full charge it was okay with 60-70 battery amps out, but towards the bottom half it was voltage sag city.